Metal-Catalyzed Radical Polyaddition for Aliphatic Polyesters via Evolution of Atom Transfer Radical Addition into Step-Growth Polymerization

The metal-catalyzed radical addition wits evolved into a step-growth polymerization by using a series of designed monomers [CH2=CH-R-OC(O)CH(CH3)Cl] that bear a reactive C-Cl and an unconjugated C=C double bond via an ester linkage and various metal catalysts to produce novel aliphatic polyesters by the metal-catalyzed radical polyaddition. The polyaddition reactions smoothly proceeded, and the conversion reached over 99% with the FeCl2/Pn-Bu-3 or CuCl/N,N,N',N '',N ''-pentamethyldiethylenetriamine system to afford the polymers in high yield. The molecular weights progressively increased with the extent of the reaction in the later stages, and the molecular weight distributions were close to 2. indicating an ideal step-growth polymerization. The well-defined polymer structures were confirmed by H-1-H-1 correlation spectroscopy NMR analysis of the products along with the model 1:1 reactions between a halide and a vinyl compound. The polyester bearing an active C-Cl terminus obtained by the radical polyaddition was employed as it macroinitiator in the metal-catalyzed living radical polymerization of vinyl monomers such as styrene, methyl methacrylate, and methyl acrylate for block copolymers consisting of polyesters and vinyl polymers.